Understanding Exposure in the Digital Age

Confusing as it is, you have to understand this and I did the hard way with rolls upon rolls of film but today, people don't seem to care as they leave their cameras running on Auto. The fundamentals of exposure are not understood in the correct context and as such, mishaps will happen the moment you go full manual.

Holy Trinity of Exposure

When I started out, the first thing I had to understand was the correlation between ISO, Shutter Speed and f/stop. I had trouble imaging this because the damn SLR I got was fully auto EOS Canon. And the compact cameras I had didn't help either as there was no way to see this in action. It was that I bought into an old used, Nikon FM2 that I finally understood how they were related.

Everything in camera exposure is related to one another. The moment you preset one value, then you will be able to see how that value affects the others. Should any one of those change, for example, the shutter speed, then the corresponding Aperture and ISO would have to change as well to reflect this. One of the best way to understand this is to fix one of the variables so that you can see these changes.

Exposure Variables through Shutter Priority and Aperture Priority

In fully auto digital camera these days, many would shoot using AUTO mode and rarely will people even venture to P or Program mode. Confusion and madness abound when either Shutter Speed or Aperture is not fixed. This way, you can see how and why it affects exposure. Every scene is dependent on the available light at that moment. This is minimum exposure required to render an image. To learn about exposure, refer to the chart above where we have prioritized either the Shutter Speed or the Aperture's f/stop number.

In the first example, by keeping the shutter speed at a constant 1/60, you will see how this affects both the ISO and Aperture. Shift the ISO up to 200, and the corresponding Aperture will have to go up to f/8 just to maintain the 1/60 shutter speed.

The second example is the same, you have the Aperture fixed at f/5.6 but when you start to shift your ISO up to 200, the shutter speed will have to change to 1/125 and so on.

Why ISO matters

This is a personal preference as some may shoot using high ISO like 1600 to 3200. The rule to remember here is that ISO will affect the quality of the image—giving it a noisy and grainy look as you go up the ISO ladder. So staying low is probably the best way to get good imaging.

Exposure stacking, which is similar to HDR photography except that you capture only three frames with a 1EV difference between them is probably one of the most effective ways to capture night time photos without high ISO. Trusted that this method works best for scenes without moving objects, I have seen this method applied to model and fashion photography in high contrast scenes. The reason for such a method is to arrest the problems of the sensor's limited dynamic range by clawing that back with a three frame shot.

High ISO is more effective in situations where there is movement and low light where exposure stacking is not possible due to movement of the subjects in the foreground or background.

Depth of Field for Bokeh

Aperture control is a deft art. You can't deny its artistic merits but you can use a cheat sheet for this. How it affects exposure and DOF (depth of field) is sublime.

As much as I love playing with the aperture, you have also got to understand that your choice of f/stop is dependent on exposure. If you want to throw something out of focus, then you need to keep the aperture wide open to let in all the light while throwing the background out of focus. Even during the analogue era, we had to get to grips with DOF for without it, the pictures would look dire. Digital is no different but there are more restrictions, something I will reserve for another article.

Master of All Exposures

Once you jump over the exposure hurdle by learning how to Aperture, Shutter Speed and ISO affect one another and in turn give you the creative edge in creating a picture, then you have ascended to a new level of photography.

These basic rules must be understood. Once you have this, you can apply various techniques found in digital cameras to further your imaging goals.

I didn't have to worry about the transition as I had already grasp the very basics of exposure and applied that to digital. For this, I hope that you will start with manual settings on your digital camera and learn to shoot with it to see the difference. I spent a fortune on film learning the outcome of my exposure experiments but you don't have to once you have a digital camera in tow. For this alone, there is no reason why you can't master this with just a few clicks.